The present invention relates to an aluminum alloy composite material for brazing, which is improved in strength, corrosion resistance and brazability, and which provides remarkable advantages when used for assembly process by brazing method with noncorrosive flux.
Aluminum alloy composite materials for brazing are used for a tube member of a brazed radiator, and the like, and conventionally, brazing sheets comprising an Al--Mn alloy (JIS A3003) core member and an Al--Si filler member clad on the core member are used for this purpose. The brazing sheet with the JIS A3003 core member, however, has a post-brazing strength of not greater than 110 N/mm.sup.2 or thereabouts and is not sufficiently resistant to corrosion.
If Mg is added to the aluminum alloy for the core member, the strength of the composite material can be improved, but this results in an increased erosion of the core member due to the filler member and also in a reduction of brazability and corrosion resistance. Particularly, in the case of employing brazing method with noncorrosive flux, the Mg content of the core member in excess of 0.2 weight % entails a substantial drop of the brazability, and accordingly, the addition of Mg to the core member of the aluminum alloy must be restricted.
There has been also presented, in Japanese Published Unexamined Patent Applications No. 175093/1990, No. 198446/1992, No. 198447/1992 and No. 198448/1992, an aluminum alloy composite material for brazing improved in the post-brazing strength without inhibiting brazability. This composite material, however, cannot achieve a satisfactory corrosion resistance when the material is made to be drawn thinner.
Thus, with conventional techniques, it is difficult to obtain a tube member of a brazed radiator which has high strength and high corrosion resistance and yet is excellent in brazability. As for heat exchanger such as an automobile radiator, thin materials are needed to reduce the weight and cost, and accordingly, there is a demand for an aluminum alloy composite material for brazing which has high strength and high corrosion resistance and is excellent in brazability, but no such material has been developed yet.